Constant velocity universal joint outer joint member and manufacturing method for same

ABSTRACT

A cup member has a cylindrical portion, a bottom portion, and a short shaft portion having a solid shaft shape and including a joining end surface at an end portion thereof. A shaft member has a solid shaft shape and includes a joining end surface at one end thereof. The joining end surfaces of the cup and shaft members are brought into abutment against each other and welded from a radially outer side to form a welded portion. At this time, center segregation is prevented from interfering with the welded portion. The cup member is formed by forging including upsetting a billet having a columnar shape successively in a plurality of stages, extruding the cylindrical portion and the short shaft portion, and ironing the cylindrical portion. In the course of the upsetting, a region of the billet corresponding to a bottom side of the cup member is narrowed.

TECHNICAL FIELD

The present invention relates to an outer joint member of a constant velocity universal joint and a method of manufacturing the outer joint member. More specifically, the present invention relates to an outer joint member of a joint type manufactured by joining a cup member and a shaft member to each other, and a method of manufacturing the outer joint member.

BACKGROUND ART

In a constant velocity universal joint, which is used to construct a power transmission system for automobiles and various industrial machines, two shafts on a driving side and a driven side are coupled to each other to allow torque transmission therebetween, and rotational torque can be transmitted at a constant velocity even when each of the two shafts forms an operating angle. The constant velocity universal joint is roughly classified into a fixed type constant velocity universal joint that allows only angular displacement, and a plunging type constant velocity universal joint that allows both the angular displacement and axial displacement. In a drive shaft configured to transmit power from an engine of an automobile to a driving wheel, for example, the plunging type constant velocity universal joint is used on a differential side (inboard side), and the fixed type constant velocity universal joint is used on a driving wheel side (outboard side).

Irrespective of the fixed type and the plunging type, the constant velocity universal joint includes, as main components, an inner joint member, an outer joint member, and torque transmission members. The outer joint member includes a cup section and a shaft section. The cup section has track grooves formed in an inner peripheral surface thereof and configured to allow the torque transmission members to roll thereon. The shaft section extends from a bottom of the cup section in an axial direction. In many cases, the outer joint member is constructed by integrally forming the cup section and the shaft section by subjecting a rod-like solid blank, that is, a round bar to plastic working such as forging and ironing or processing such as cutting work, heat treatment, and grinding (see FIG. 4 and FIG. 8 of Patent Literature 1).

In Patent Literature 1, there is disclosed steps of manufacturing an outer joint member, which integrally includes a cup member and a shaft member, through forging. The forging is described with reference to FIG. 26a to FIG. 26e . First, a rod-like blank, that is, a billet 170 (FIG. 26a ) is subjected to forward extrusion molding so that a preform 172 (FIG. 26b ), which includes a shaft section 174 and a solid main body section 176, is obtained. Next, the solid main body section 176 is subjected to upsetting so that an intermediate preform 178 (FIG. 26c ), which is constructed by the shaft section 174 and a solid large-diameter section 180, is obtained. Next, the solid main body section 178 is subjected to backward extrusion and formed into a cup section 184, which is literally opened at one end, so that a preforged product 182 (FIG. 26d ) is obtained. After that, the cup section 184 of the preforged product 182 is subjected to ironing so that an ironed product 186 (FIG. 26e ) that is finished with high accuracy is obtained. In the course of the backward extrusion and ironing, on an inner side of the cup section, there are formed track grooves 188 serving as rolling surfaces for torque transmission balls in the case of a ball type constant velocity universal joint, and there are formed track grooves (not shown) in the case of a tripod type constant velocity universal joint.

The shaft section 174 molded by the forward extrusion (FIG. 26b ) is retained by a lower portion molding die (not shown) throughout all of subsequent steps of upsetting (FIG. 26c ), backward extrusion (FIG. 26d ), and ironing (FIG. 26e ). Further, the upsetting is performed in a single step (FIG. 26c ).

Incidentally, an outer joint member (long stem type) including a shaft section longer than a standard may sometimes be used. For example, in order to equalize lengths of a right part and a left part of the drive shaft, the long stem type is used for a constant velocity universal joint on the inboard side that corresponds to one side of the drive shaft. In this case, the shaft section is rotatably supported by a support bearing. Although varied depending on vehicle types, the length of the shaft section of the long stem type is approximately from 300 mm to 400 mm in general. The outer joint member of the long stem type has a long shaft section, and hence there is a difficulty in integrally forming the cup section and the shaft section with high accuracy. Therefore, there is known an outer joint member in which the cup section and the shaft section are formed as separate members, and both the members are joined through friction press-contact (Patent Literature 2).

An overview of the friction press-contact technology for the outer joint member described in Patent Literature 2 is described below. First, as illustrated in FIG. 27, a cup member 72 and a shaft member 73 are joined through the friction press-contact to form an intermediate product 71′. Next, burrs 75 on a radially outer side of a joining portion 74 are removed, and hence an outer joint member 71 as illustrated in FIG. 28 is obtained. The burrs 75 are generated on the joining portion 74 of the intermediate product 71′ along with the press-contact. The burrs 75 on the radially outer side of the joining portion 74 are removed through processing such as turning. Accordingly, a support bearing (rolling bearing 6: see FIG. 1) to a shaft section of the outer joint member 71.

Although illustration is omitted, the intermediate product 71′ is processed into a finished product of the outer joint member 71 through machining of a spline, snap ring grooves, and the like, and through heat treatment, grinding, and the like. Therefore, the outer joint member 71 and the intermediate product 71′ have slight differences in shape. However, illustration of the slight differences in shape is omitted in FIG. 27 and FIG. 28 to simplify the description, and the outer joint member 71 being the finished product and the intermediate product 71′ are denoted by the reference symbols at the same parts. The same applies to the description below.

CITATION LIST

Patent Literature 1: JP 11-179477 A

Patent Literature 2: JP 2012-057696 A

Patent Literature 3: JP 2013-100859 A

SUMMARY OF INVENTION Technical Problem

The burrs 75 on the joining portion 74, which are generated due to the friction press-contact, not only are quenched by friction heat and cooling that follows the friction heat to have a high hardness but also have a distorted shape extended in an axial direction and a radial direction. Therefore, when removing the burrs 75 on the radially outer side through the turning, a tip for turning is liable to be significantly abraded due to the high hardness and cracked due to the distorted shape. Therefore, it is difficult to increase the turning speed. In addition, a cutting amount per pass of the tip for turning is decreased, and hence the number of passes is increased, which causes a problem in that the cycle time is increased to increase the manufacturing cost.

Further, in order to inspect a joining state of the joining portion 74 of the outer joint member 71, when ultrasonic flaw detection, which enables flaw detection at high speed, is to be performed, an ultrasonic wave is scattered due to the burrs 75 remaining on the radially inner side of the joining portion 74, and hence the joining state cannot be checked. Therefore, there occurs a problem in that total inspection through the ultrasonic flaw detection cannot be performed after the joining.

In view of the above-mentioned problems, when welding through use of high energy intensity beam such as laser welding or electron beam welding is employed, it is conceivable that the surfaces of the joining portion may be prevented from being increased in thickness unlike the case of the friction press-contact (see Patent Literature 3). However, when the cup member 72 and the shaft member 73 as illustrated in FIG. 29 are brought into abutment against each other to be welded, a hollow cavity portion 76 having a relatively large volume is formed. Then, a pressure in the hollow cavity portion 76 is increased due to processing heat during the welding, and after completion of the welding, the pressure is decreased. Due to such variation in the internal pressure of the hollow cavity portion 76, blowing of a molten material occurs. Thus, there arise defects such as formation of a recess on a surface of the welded portion, poor penetration depth, and generation of air bubbles inside the welded portion, thereby degrading the welding state. As a result, the strength of the welded portion is not stable, which adversely affects quality.

Further, in consideration of the case where members (workpieces) constructing the outer joint member of the constant velocity universal joint are to be welded, the workpieces employ medium to high carbon steel having a high carbon content to secure strength. Thus, when the workpieces are welded to each other as they are, the welded portion is significantly hardened, and becomes more liable to be cracked. Therefore, for the purpose of reducing the hardness and securing the toughness, pre-heating is performed to reduce the cooling rate after welding. However, when the workpieces each having a solid shaft shape are butt-welded as they are, a large volume in the periphery of the welded portion may cause a long time for pre-heating to be required. Thus, the cycle time is increased to increase the manufacturing cost.

Further, in the case of a joint-type outer joint member manufactured by joining the cup member and the shaft member through welding, when, in particular, center segregation of the rod-like blank being a blank for the cup member enters the welded portion, impurities may reduce strength of the joined portion and increase the percent defective. Herein, the segregation is a phenomenon of causing uneven distribution of alloying elements or impurities, or such a state (JIS G 0201 Terms used in iron and steel (Heat Treatment)). Further, the center segregation represents occurrence of segregation at a center portion of a steel material due to segregation of components in a solidifying step of steel (see JIS G 0553 Macroscopic examination method for steel).

The outer joint member disclosed in Patent Literature 1 is of a type integrally including the cup section and the shaft section. Thus, the problems which may arise in the case of welding the cup section and the shaft section are not considered. However, when the upsetting is performed in a single step as in the forging disclosed in Patent Literature 1, the section reduction rate or the height reduction rate is increased. There is a limit in the lateral expansion in a billet end surface due to friction with a die or a punch, and hence a center portion of the billet in a height direction is laterally expanded (increased in diameter). As a result, the center segregation also moves toward the radially outer side. There is a fear in that the center segregation having moved toward the radially outer side in such a manner may interfere with the joined portion in the case of the joint-type outer joint member. The interference of the center segregation with the joined portion may cause poor strength and defective welding. Thus, elaboration of confining the center segregation within the radially inner side is required in the step of forging so as to prevent the interference of the center segregation with the welded portion. The section reduction rate is represented by 100×(A₀−A)/A, where a sectional area before molding of a material is A₀, and a sectional area after molding is A. Further, the height reduction rate is a percentage calculated by 100×(H₀−H)/H, where the height of a material portion, which is to be subjected to upsetting, before processing is H₀, and the height after processing is H (JIS B 0112 Terms of forging).

It is conceivable to use a material having a high cleanliness. However, the use of such material increases the cost. Further, when a stem having a small diameter is not to be employed to avoid the interference of the center segregation, the design is limited at the time of considering a stem shape of the joint-type outer joint member, which is not preferred.

It is an object of the present invention to eliminate the above-mentioned problems of the above-mentioned related art, and to improve strength and quality of a welded portion of an outer joint member of a constant velocity universal joint which is manufactured by joining a cup member and a shaft member through welding.

Solution to Problem

In order to solve the above-mentioned problem, according to one embodiment of the present invention, there is provided an outer joint member of a constant velocity universal joint, comprising: a cup member; and a shaft member, the outer joint member being manufactured by joining the cup member and the shaft member, the cup member having a bottomed cylindrical shape that is opened atone end, and comprising a cylindrical portion, a bottom portion, and a short shaft section protruding from the bottom portion, the short shaft portion having a solid shaft shape, and comprising a joining end surface at an end portion thereof, the shaft member having a solid shaft shape, and comprising a joining end surface at one end thereof, the joining end surface of the cup member and the joining end surface of the shaft member being brought into abutment against each other and welded to form a welded portion having an annular shape, to prevent interference of center segregation with the welded portion.

The welded portion is formed into an annular shape, and hence the welded portion is positioned on a radially outer side with respect to the center segregation. Thus, the problem caused by the interference of the center segregation with the welded portion is eliminated. The range of the center segregation is not determined geometrically. However, herein, the range of the center segregation in the radial direction is assumed to be within the range of one-half of the diameter of the blank, and such range is determined based on the impact test piece location of a round bar defined by JIS G 0416 (Steel and Steel Products—Location and Preparation of Samples and Test Pieces for mechanical testing) and with expectation for safety.

The welded portion is a generic name of a portion including a welded metal and a heat-affected portion. The welded metal is metal which forms part of the welded portion and is molten and solidified during welding. The heat-affected portion is a portion which is changed in structure, metallurgical property, mechanical property, and the like by heat of welding and is unmolten part of a base material (JIS Z 3001-1 Welding Terms—Section 1: General).

Herein, the term “solid shaft shape” is intended to exclude a shaft having a hollow cavity penetrating in an axial direction, or a shaft having an elongated hollow cavity portion extending from a joining end surface in the axial direction (see Patent Literatures 2 and 3). The cup member has a bottomed cylindrical shape as a whole, but the short shaft section having the joining end surface formed thereon does not have a through hole and an elongated hollow cavity portion extending from the joining end surface in the axial direction. Thus, at least the short shaft section has a solid shaft shape.

According to one embodiment of the present invention, there is provided a method of manufacturing an outer joint member of a constant velocity universal joint, when the above-mentioned outer joint member of a constant velocity universal joint is to be manufactured, the method comprising: forming the cup member by forging, the forging comprising: upsetting a billet having a columnar shape successively in a plurality of stages; extruding the cylindrical portion and the short shaft portion; and ironing the cylindrical portion; and bringing a joining end surface of the cup member and a joining end surface of the shaft member into abutment against each other and welding the joining end surfaces to form a welded portion having an annular shape.

Advantageous Effects of Invention

In the outer joint member of a constant velocity universal joint according to the present invention, the welded portion has an annular shape. Thus, even when the center segregation occurs in the blank, the interference of the center segregation with the welded portion can be avoided as much as possible. Therefore, welding quality for the joint-type outer joint member including the cup member and the shaft member joined through welding is improved, thereby being capable of securing strength of the welded portion.

With the method of manufacturing an outer joint member of a constant velocity universal joint according to the present invention, the center segregation near the joining end surface of the cup member is confined within the radially inner side, thereby being capable of avoiding the interference of the center segregation with the welded portion as much as possible, suppressing the reduction in strength of the welded portion, and reducing the percent defective. Further, the interference of the center segregation with the welded portion can be avoided as much as possible. Thus, the method is applicable also to the case of the cup member having a relatively small diameter, and hence the degree of freedom in design of the outer joint member may be attained.

In welding with a high energy intensity beam, a bead width is small, and deep penetration can be obtained in a short period of time, thereby being capable of increasing the strength of the welded portion and reducing thermal strain. Further, burrs are not generated, and hence post-processing for the joining portion can be omitted. As a result, the manufacturing cost can be reduced. Further, there is no scattering of ultrasonic waves caused by the burrs, which is a problem raised in the case of joining through the friction press-contact. Thus, total inspection through ultrasonic flaw detection can be performed to stably secure high welding quality. Further, in general, the electron beam welding is performed in vacuum. Therefore, the problems such as the blowing of a molten material and the generation of air bubbles are eliminated.

As is clear from the description above, according to the method of butt-welding of the present invention, the strength and quality of the welded portion can be improved. Further, when the present invention is applied to manufacturing of an outer joint member of a constant velocity universal joint having the cup member and the shaft member joined through butt-welding, the outer joint member improved in strength and quality of the welded portion can be provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a partial sectional front view of a drive shaft including a plunging type constant velocity universal joint with an outer joint member of a long stem type.

FIG. 2a is an enlarged view for illustrating a first embodiment of the outer joint member of FIG. 1.

FIG. 2b is an enlarged view of a portion “b” of FIG. 2 a.

FIG. 2c is an enlarged view, which is similar to FIG. 2b , for illustrating a state before welding.

FIG. 3 is a block line diagram for illustrating manufacturing steps for the outer joint member of FIG. 1.

FIG. 4a is a vertical sectional view of a cup member after ironing.

FIG. 4b is a vertical sectional view of the cup member after turning.

FIG. 5a is a front view of a bar material being a blank of a shaft member.

FIG. 5b is a partial sectional front view after forging.

FIG. 5c is a partial sectional front view of the shaft member after turning and spline processing.

FIG. 6 is a schematic elevation view of a welding apparatus before welding.

FIG. 7 is a schematic elevation view of the welding apparatus during welding.

FIG. 8 is a schematic elevation view of an ultrasonic flaw-detection apparatus.

FIG. 9 is a schematic plan view of the ultrasonic flaw-detection apparatus.

FIG. 10 is a schematic elevation view of the ultrasonic flaw-detection apparatus.

FIG. 11 is a schematic plan view of the ultrasonic flaw-detection apparatus.

FIG. 12a is a partial enlarged sectional view taken along the line XII-XII of FIG. 10 in a case of a non-defective welded product.

FIG. 12b is a partial enlarged sectional view taken along the line XII-XII of FIG. 10 in a case of a defective welded product.

FIG. 13 is a partial enlarged sectional view, which is similar to FIG. 12a and FIG. 12b , for illustrating findings in the course of development.

FIG. 14 is a partial sectional front view for illustrating a shaft member assigned with a different product number.

FIG. 15 is a partial sectional front view of an outer joint member that is manufactured using the shaft member of FIG. 14.

FIG. 16 is a block line diagram for illustrating an example of standardization of a product type of the cup member.

FIG. 17a is a partial sectional front view for illustrating a second embodiment of the outer joint member.

FIG. 17b is an enlarged view of a portion “b” of FIG. 17 a.

FIG. 17c is an enlarged view, which is similar to FIG. 17b , for illustrating a state before welding.

FIG. 18 is a vertical sectional view of the cup member of FIG. 17 a.

FIG. 19 is a block line diagram for illustrating a second embodiment of a method of manufacturing an outer joint member.

FIG. 20 is a block line diagram for illustrating a third embodiment of the method of manufacturing the outer joint member.

FIG. 21 is a partial sectional front view for illustrating a constant velocity universal joint of the third embodiment of the outer joint member.

FIG. 22 is a partial sectional front view of the outer joint member of FIG. 21.

FIG. 23a is a view for illustrating a forging step according to the embodiment.

FIG. 23b is a view for illustrating the forging step according to the embodiment.

FIG. 23c is a view for illustrating the forging step according to the embodiment.

FIG. 23d is a view for illustrating the forging step according to the embodiment.

FIG. 23e is a view for illustrating the forging step according to the embodiment.

FIG. 23f is a view for illustrating the forging step according to the embodiment.

FIG. 23g is a view for illustrating the forging step according to the embodiment.

FIG. 24a is a partial sectional view for illustrating an example of a sectional shape of a die.

FIG. 24b is a partial sectional view for illustrating the example of the sectional shape of the die.

FIG. 24c is a partial sectional view for illustrating the example of the sectional shape of the die.

FIG. 25a is a view for illustrating a forging step according to Comparative Example.

FIG. 25b is a view for illustrating the forging step according to Comparative Example.

FIG. 25c is a view for illustrating the forging step according to Comparative Example.

FIG. 25d is a view for illustrating the forging step according to Comparative Example.

FIG. 25e is a view for illustrating the forging step according to Comparative Example.

FIG. 25f is a view for illustrating the forging step according to Comparative Example.

FIG. 26a is a view for illustrating a forging step according to a related art.

FIG. 26b is a view for illustrating the forging step according to the related art.

FIG. 26c is a view for illustrating the forging step according to the related art.

FIG. 26d is a view for illustrating the forging step according to the related art.

FIG. 26e is a view for illustrating the forging step according to the related art.

FIG. 27 is a vertical sectional view of an intermediate product of an outer joint member for illustrating the related art.

FIG. 28 is a vertical sectional view of the outer joint member for illustrating the related art.

FIG. 29 is a vertical sectional view of an outer joint member for illustrating another related art.

DESCRIPTION OF EMBODIMENTS

Now, description is made of embodiments of the present invention with reference to the drawings.

First, a first embodiment of an outer joint member is described with reference to FIG. 1 and FIG. 2a to FIG. 2c , and subsequently, a first embodiment of a method of manufacturing the outer joint member is described with reference to FIG. 3 to FIG. 16.

FIG. 1 is a view for illustrating the entire structure of a drive shaft 1. The drive shaft 1 mainly comprises a plunging type constant velocity universal joint 10, a fixed type constant velocity universal joint 20, and an intermediate shaft 2 configured to couple both the joints 10 and 20. The plunging type constant velocity universal joint 10 is arranged on a differential side (right side of FIG. 1: hereinafter also referred to as “inboard side”), and the fixed type constant velocity universal joint 20 is arranged on a driving wheel side (left side of FIG. 1: hereinafter also referred to as “outboard side”).

The plunging type constant velocity universal joint 10 is a so-called double-offset type constant velocity universal joint (DOJ), and mainly comprises an outer joint member 11, an inner joint member 16, a plurality of balls 41 serving as torque transmitting elements, and a cage 44 configured to retain the balls 41.

The outer joint member 11 comprises a cup section 12 and a long shaft section (hereinafter also referred to as “long stem section”) 13 that extends from a bottom of the cup section 12 in an axial direction. The inner joint member 16 is housed in the cup section 12 of the outer joint member 11. Track grooves 30 formed along an inner periphery of the cup section 12 of the outer joint member 11 and track grooves 40 formed along an outer periphery of the inner joint member 16 form pairs, and the balls 41 are arranged between the track grooves 30 and 40 of respective pairs. The cage 44 is interposed between the outer joint member 11 and the inner joint member 16, and is held in contact with a partially cylindrical inner peripheral surface 42 of the outer joint member 11 at a spherical outer peripheral surface 45 and held in contact with a spherical outer peripheral surface 43 of the inner joint member 16 at a spherical inner peripheral surface 46. A curvature center O₁ of the spherical outer peripheral surface 45 and a curvature center O₂ of the spherical inner peripheral surface 46 of the cage 44 are offset equidistantly from a joint center O toward opposite sides in the axial direction.

An inner ring of a support bearing 6 is fixed to an outer peripheral surface of the long stem section 13, and an outer ring of the support bearing 6 is fixed to a transmission case with a bracket (not shown). As described above, the outer joint member 11 is supported by the support bearing 6 in a freely rotatable manner, and hence vibration of the outer joint member 11 during driving or the like is prevented as much as possible.

The fixed type constant velocity universal joint 20 is a so-called Rzeppa type constant velocity universal joint, and mainly comprises an outer joint member 21, an inner joint member 22, a plurality of balls 23 serving as torque transmitting elements, and a cage 24 configured to retain the balls 23. The outer joint member 21 comprises a bottomed cylindrical cup section 21 a and a shaft section 21 b that extends from a bottom of the cup section 21 a in the axial direction. The inner joint member 22 is housed in the cup section 21 a of the outer joint member 21. The balls 23 are arranged between the cup section 21 a of the outer joint member 21 and the inner joint member 22. The cage is interposed between an inner peripheral surface of the cup section 21 a of the outer joint member 21 and an outer peripheral surface of the inner joint member 22.

Note that, as the fixed type constant velocity universal joint, an undercut-free type constant velocity universal joint may sometimes be used.

The intermediate shaft 2 comprises spline (including serrations; the same applies hereinafter) shafts 3 on both end portions thereof. The spline shaft 3 on the inboard side is inserted to a spline hole of the inner joint member 16 of the plunging type constant velocity universal joint 10. Thus, the intermediate shaft 2 and the inner joint member 16 of the plunging type constant velocity universal joint 10 are coupled to each other to allow torque transmission therebetween. Further, the spline shaft 3 on the outboard side is inserted to a spline hole of the inner joint member 22 of the fixed type constant velocity universal joint 20. Thus, the intermediate shaft 2 and the inner joint member 22 of the fixed type constant velocity universal joint 20 are coupled to each other to allow torque transmission therebetween. Although the example of the solid intermediate shaft 2 is illustrated, a hollow intermediate shaft may also be used.

Grease is sealed inside both the constant velocity universal joints 10 and 20 as a lubricant. To prevent leakage of the grease or entry of a foreign matter, bellows boots 4 and 5 are respectively mounted to a portion between the outer joint member 11 of the plunging type constant velocity universal joint 10 and the intermediate shaft 2, and a portion between the outer joint member 21 of the fixed type constant velocity universal joint 20 and the intermediate shaft 2.

Next, details of the outer joint member 11 are described with reference to FIG. 2a to FIG. 2 c.

The outer joint member 11 comprises the cup section 12 and the long stem section 13. The outer joint member 11 is manufactured by joining the cup member 12 a and the shaft member 13 a through butt welding, and manufacturing steps are described later in detail.

The cup section 12 has a bottomed cylindrical shape that is opened at one end, and the inner peripheral surface 42 has the plurality of track grooves 30 that are formed equidistantly in a circumferential direction, thereby forming a partially cylindrical shape. The balls 41 (see FIG. 1) roll on the track grooves 30.

The cup member 12 a is an integrally-formed product being made of medium carbon steel, e.g., S53C, containing carbon of from 0.40 wt % to 0.60 wt %, and having a cylindrical portion 12 a 1 and a bottom portion 12 a 2. The cylindrical portion 12 a 1 has the track grooves 30 and the inner peripheral surface 42 described above. A boot mounting groove 32 is formed at an outer periphery of the cup member 12 a on the opening side thereof, whereas a snap ring groove 33 is formed at an inner periphery. The bottom portion 12 a 2 has a shaft section having a solid shaft shape protruding toward the shaft member 13 a side, that is, a short shaft section 12 a 3, and a joining end surface 50 (FIG. 2c ) is formed at the short shaft section 12 a 3.

The joining end surface 50 is finished by turning. Herein, a recessed portion 50 b is formed on a radially inner side of the joining end surface 50, and as a result, the annular joining end surface 50 is formed on a radially outer side of the recessed portion 50 b. The reference symbol D denotes an inner diameter of the joining end surface 50. The recessed portion 50 b may be formed during forging, or may be formed by cutting. When the recessed portion 50 b is formed during forging, the number of steps can be reduced. Further, the joining end surface 50 is formed into an annular shape, and hence time required for turning can be reduced.

The long stem section 13 is a solid shaft that extends from the bottom portion 12 a 2 of the cup section 12 in the axial direction. A bearing mounting surface 14 and a snap ring groove 15 are formed at an outer periphery of the long stem section 13 on the cup member 12 a side, whereas a spline shaft Sp serving as a torque transmission coupling portion is formed at an end portion on a side opposite to the cup section 12.

The shaft member 13 a is made of medium carbon steel, e.g., S40C, containing carbon of from 0.30 wt % to 0.55 wt %. A joining end surface 51 (FIG. 2c ) is formed at an end portion on the cup member 12 a side. The joining end surface 51 has a recess 52, and as a result, is formed into an annular surface. The reference symbol E denotes an inner diameter of the joining end surface 51. FIG. 2a to FIG. 2c and FIG. 5a to FIG. 5c are illustrations of an example in which the recess 52 is formed during forging and in which the inner diameter portion 53 is formed in the joining end surface 51 by cutting. Thus, it appears as if the recess 52 and the inner diameter portion 53 are formed into a hole having stages. However, the inner diameter portion 53 may be an inner diameter portion of the joining end surface 51, or may be an inner diameter portion of the recess 52. The recess 52 may maintain a forged surface. In that case, the inner diameter portion 53 that can be clearly distinguished from the recess 52 does not appear as illustrated.

The recess 52 has a shallow bottom, that is, is very shallow with respect to an outer diameter of the joining end surface 51. As an example of the depth, a lower limit is approximately 1 mm. That is intended to secure a straight portion having a length in the axial direction necessary to perform ultrasonic flaw detection for defectiveness in dimension in the radial direction (penetration depth) of the welded portion 49. The above-mentioned lower limit is a value in view of the ultrasonic flaw detection. In view of reducing the pre-heating time through reduction of a volume near the joining portion, a corresponding depth of the recess 52 is desired.

In the case of forming the recessed portion during forging, an upper limit of the depth of the recess 52 is approximately a limit value formed through forging (reference)×1.5 mm. Excessively deep recess 52 may cause increase in forging load, degradation of die lifetime, and increase in processing cost. Even in the case of forming through cutting, excessively deep recess 52 may cause longer processing time and poor material yield.

The inner diameter portion 53 of the joining end surface 51, while being dependent on the outer diameter of the shaft member 13 a, is presupposed to secure a radial width of the welded portion 49 to be formed on the outer diameter side of the recess 52. The term “diameter” of the inner diameter is generally associated with a circular shape. However, a contour of the recess 52 as viewed from a plane perpendicular to the axial line of the shaft member 13 a is not limited to have a circular shape, and the shape may be, for example, a polygon or an irregular shape.

Welding is performed by bringing the joining end surface 50 of the cup member 12 a and the joining end surface 51 of the shaft member 13 a into abutment against each other and irradiating an electron beam from an outer side of the cup member 12 a in the radial direction (FIG. 2a and FIG. 2b ). The welded portion 49, as is well known, comprises metal that is molten and solidified during welding, that is, a molten metal and a heat-affected portion in a periphery of the molten metal. In FIG. 2b , the broken parallel oblique lines schematically represent an assumed range S of the center segregation. As illustrated in FIG. 2b , the assumed range S of the center segregation is confined within the radially inner side to prevent the interference with the welded portion 49. With regard to the shaft member 13 a, illustration of the assumed range of the center segregation is omitted. This is because, even in the case of molding the recess 52 at an end portion through forging such as upset forging (see FIG. 5a to FIG. 5c ), the recess 52 is as shallow as counter boring as described above, and hence the section reduction rate and the height reduction rate are small, with the result that the recess 52 is not increased in diameter to such an extent that the assumed range of the center segregation interferes with the welded portion.

Although detailed description is made later, outer diameters B of the joining end surfaces 50 and 51 (see FIG. 4b and FIG. 5c ) are set to equal dimensions for each joint size. However, the outer diameter B of the joining end surface 50 of the cup member 12 a and the outer diameter B of the joining end surface 51 of the shaft member 13 a need not be set to equal dimensions. In consideration of, for example, a state of the bead, a dimensional difference may be given as appropriate in such a manner that the outer diameter B of the joining end surface 51 is set slightly smaller than the outer diameter B of the joining end surface 50 or the like. The dimensional relationship between the outer diameter B of the joining end surface 50 and the outer diameter B of the joining end surface 51 is the same throughout the Description.

The welded portion 49 is formed on the cup member 12 a side with respect to the bearing mounting surface 14 of the shaft member 13 a, and hence the bearing mounting surface 14 and the like can be processed in advance before welding so that post-processing after welding can be omitted. Further, in the electron beam welding, burrs are not generated at the welded portion. Thus, also on this point, post-processing for the welded portion can also be omitted, which can reduce manufacturing cost. Still further, total inspection on the welded portion through ultrasonic flaw detection can be performed.

As illustrated in FIG. 2c , an inner diameter D of the joining end surface 50 of the cup member 12 a is set smaller than an inner diameter E of the joining end surface 51 of the shaft member 13 a. As a result, the joining end surface 50 of the cup member 12 a partially protrudes to a radially inner side with respect to the joining end surface 51 having the inner diameter E. This protruding portion is referred to as a protruding surface 50 a. The joining end surfaces 50 and 51 having such a shape are brought into abutment against each other, and the cup member 12 a and the shaft member 13 a are joined by welding. The protruding surface 50 a is formed to be the same for each joint size.

Next, the manufacturing method of the above-mentioned outer joint member is described with reference to FIG. 3 to FIG. 16. Before description of details of each manufacturing step, an overview of manufacturing steps is described.

As illustrated in FIG. 3, the cup member 12 a is manufactured through manufacturing steps comprising a bar material cutting step S1 c, a forging step S2 c, an ironing step S3 c, and a turning step S4 c. The forging step S2 c and the ironing step S3 c are illustrated as separate steps. However, in general, the forging operation is classified variously, and there is a case where the steps including upsetting, extruding, and ironing are collectively referred to as forging (see FIG. 23 and corresponding description).

Meanwhile, the shaft member 13 a is manufactured through manufacturing steps comprising a bar material cutting step S1 s, a turning step S2 s, and a spline processing step S3 s.

The cup member 12 a and the shaft member 13 a thus manufactured are each assigned with a product number for management. After that, the cup member 12 a and the shaft member 13 a are subjected to a welding step S6, an ultrasonic flaw detection step S6 k, a heat treatment step S7, and a grinding step S8 so that the outer joint member 11 is completed.

An overview of each step is described below. Each step is described as a typical example, and appropriate modification and addition may be made as needed.

First, the manufacturing steps for the cup member 12 a are described.

[Bar Material Cutting Step S1 c]

A bar material (round bar) is cut into a predetermined length in accordance with a forging weight, thereby producing a columnar billet.

[Forging Step S2 c]

The billet is subjected to forging so as to integrally form the cylindrical portion, the bottom portion, and the projecting portion as a preform of the cup member 12 a.

[Ironing Step S3 c]

Ironing is performed on the track grooves 30 and the cylindrical surface 42 of the preform, thereby finishing the inner periphery of the cylindrical portion of the cup member 12 a.

[Turning Step S4 c]

In the preform after ironing, the outer peripheral surface, the boot mounting groove 32, the snap ring groove 33 and the like, and the joining end surface 50 are formed by turning. After the turning step S4 c, the cup member 12 a in the form of an intermediate component is assigned with a product number for management.

Next, the manufacturing steps for the shaft member 13 a are described.

[Bar Material Cutting Step S1 s]

A bar material is cut into a predetermined length in accordance with an entire length of the shaft section, thereby producing a columnar billet. After that, the billet is forged into a rough shape by upset forging depending on the shape of the shaft member 13 a.

[Turning Step S2 s]

The outer peripheral surface of the billet (bearing mounting surface 14, snap ring groove 15, minor diameter of the spline, end surface, and the like) and the joining end surface 51 of the billet at the end portion on the cup member 12 a side are formed by turning.

[Spline Processing Step S3 s]

The spline shaft is formed by processing splines in the shaft member through rolling after turning. Note that, the method of processing the spline is not limited to the rolling, and press working or the like may be adopted instead as appropriate. After the spline processing, the shaft member 13 a in the form of an intermediate component is assigned with a product number for management.

Next, the manufacturing steps in the process of completing the outer joint member 11 from the cup member 12 a and the shaft member 13 a in the form of the intermediate component obtained in the manner described above are described.

[Welding Step S6]

The joining end surface 50 of the cup member 12 a and the joining end surface 51 of the shaft member 13 a are brought into abutment against and welded to each other. This welding step is described later in detail.

[Ultrasonic Flaw Detection Step S6 k]

The welded portion 49 between the cup member 12 a and the shaft member 13 a is inspected by ultrasonic flaw detection. This ultrasonic flaw detection step is also described later in detail.

[Heat Treatment Step S7]

High frequency quenching and tempering are performed as heat treatment on at least the track grooves 30 and the inner peripheral surface 42 of the cup section 12 after welding and a necessary range of the outer periphery of the shaft member 13 after welding. Heat treatment is not performed on the welded portion 49. A hardened layer having a hardness of approximately from 58 HRC to 62 HRC is formed on each of the track grooves 30 and the inner peripheral surface 42 of the cup section 12 by the heat treatment. Further, a hardened layer having a hardness of approximately from 50 HRC to 62 HRC is formed in a predetermined range of the outer periphery of the shaft section 13.

[Grinding Step S8]

After the heat treatment, the bearing mounting surface 14 of the shaft member 13 and the like are finished by grinding. Thus, the outer joint member 11 is completed.

As described above, the heat treatment step is provided after the welding step, and hence the manufacturing steps are suited to a cup member and a shaft member having such shapes and specifications that the hardness of the heat-treated portion may be affected by temperature rise at the periphery due to heat generated during the welding.

Main constituent features of the above-mentioned method of manufacturing the outer joint member are described more in detail.

FIG. 23a to FIG. 23g are illustrations of the forging step for the cup member 12 a. FIG. 23a to FIG. 23g are sectional views, but illustrations of sections of the billet and the forged workpiece are omitted. Further, as already described in relation to FIG. 2b , those are schematic illustrations of the assumed range S of the center segregation with the broken parallel oblique lines. Further, the two-dotted chain lines represent a contour of the billet and the forged workpiece in the previous stage.

First, a rod-like blank (billet) 60 illustrated in FIG. 23a is inserted into a cavity of a forging die (hereinafter referred to as “die”) 62A. Then, as illustrated in FIG. 23b , a punch 66A is lowered to upset the billet 60 in the die 62A. At this time, an upper portion of the billet 60, that is, a region corresponding to an opening side of the cup member 12 a is laterally expanded (increased in diameter) until an outer diameter is regulated by an inner peripheral surface of the die 62A.

Meanwhile, a lower portion of the billet 60, that is, a region corresponding to a bottom side of the cup member 12 a is narrowed in the die 62A and reduced in diameter. In order to achieve the narrowing, an inner diameter of the die is gradually reduced as approaching the bottom side (lower side in FIG. 23) of the cup member 12 a. Specifically, as illustrated in FIG. 24a to FIG. 24c , the shapes of the inner peripheral surfaces of the dies 62A to 62C in sectional view are formed into, for example, an arc shape 64A (FIG. 24a ), a taper shape 64B (FIG. 24b ), or a combined shape 64C (FIG. 24c ) of those. The narrowing is not limited to a single step, and may be performed for a plurality of times depending on design of steps. When the narrowing is performed in such a manner, in the region corresponding to the bottom side of the cup member 12 a, a force toward a center is applied to the material through the course of upsetting (FIG. 23b to FIG. 23d ), and hence movement of the material toward the radially outer side is suppressed.

As described above, in the dies 62 (62A to 62C) to be used in the course of upsetting, an inner diameter is larger than an outer diameter of the billet 60 in a first region corresponding to the opening side of the cup member 12 a, and an inner diameter is gradually reduced in a second region corresponding to the bottom side of the cup member 12 a. Through sequential use of the plurality of dies 62A to 62C gradually increased in inner diameter in the first region, the region of the billet 60 corresponding to the opening side of the cup member 12 a is increased in diameter in the course of upsetting, thereby narrowing the region corresponding to the bottom side of the cup member 12 a.

FIG. 23b to FIG. 23d are illustrations of an example of performing the upsetting in three steps. As illustrated in FIG. 23b to FIG. 23d , the inner diameters of the dies 62A to 62C and the outer diameters of the punches 66A to 66C are sequentially increased. When the upsetting is performed in a plurality of steps, an increase in the friction resistance due to shortage of lubricant is avoided, thereby being capable of promoting the lateral expansion of the material. Thus, a billet edge can be moved to the radially outer side as much as possible. Through movement of the billet edge toward the radially outer side as much as possible, the billet edge portion can be removed at the time of subjecting the end surface on the opening side of the cup member to finishing.

Next, as illustrated in FIG. 23e , combination extrusion is performed. That is, a short shaft portion 12 a 3 of the cup member 12 a is molded by the forward extrusion, and a cylindrical portion 12 a 1 of the cup member 12 a is molded by the backward extrusion. At that time, the narrowed region corresponding to the bottom side of the cup member 12 a is retained as an original shape of the short shaft portion 12 a 3, and the backward extrusion is performed for the region of the cylindrical portion 12 a 1 corresponding to the opening side of the cup member 12 a while suppressing the lateral expansion (increase in diameter) as much as possible. In other words, a fiber flow in the axial direction is formed in the short shaft portion 12 a 3. This step may be performed for a plurality of times depending on the design of steps.

After that, as illustrated in FIG. 23f and FIG. 23g , the cylindrical portion 12 a 1 of the cup member 12 a is subjected to cold ironing so that an ironed product is obtained. The ironed product is subjected to turning as needed and formed into the cup member 12 a being a forged product (see FIG. 4a ).

FIG. 25a to FIG. 25f are schematic illustrations of shapes the workpiece which are assumed in the case of performing normal forging through upsetting, extruding, and ironing without the narrowing described in relation to FIG. 23b to FIG. 23d , for comparison with FIG. 23a to FIG. 23 g.

FIG. 4a is an illustration of a state after ironing of the cup member 12 a. FIG. 4b is an illustration of a state after turning. In a preform 12 a′ for the cup member 12 a, there are integrally formed a cylindrical portion 12 a 1′, a bottom portion 12 a 2′, and a short shaft section 12 a 3′ in the forging step S2 c (upsetting of FIG. 23b to FIG. 23d ). After that, the track grooves 30 and the cylindrical surface 42 are formed by ironing in the ironing step S3 c (FIG. 23f and FIG. 23g ) so that the inner periphery of the cylindrical portion 12 a 1′ is finished as illustrated in FIG. 4a . After that, in the turning step S4 c, the outer peripheral surface, the boot mounting groove 32, the snap ring groove 33, and the like of the cup member 12 a as well as the joining end surface 50 of the short shaft section 12 a 3 and the outer diameter B and the inner diameter D of the joining end surface 50 are formed by turning as illustrated in FIG. 4 b.

FIG. 5a and FIG. 5b are illustrations of states of the shaft member 13 a in the respective processing steps. That is, FIG. 5a is an illustration of a billet 13 a″ obtained by cutting a bar material. FIG. 5b is an illustration of a preform 13 a′ obtained by forging the billet 13 a″ into a rough shape by upset forging. FIG. 5c is an illustration of the shaft member 13 a after turning and spline processing.

The billet 13 a″ illustrated in FIG. 5a is formed in the bar material cutting step S1 s. The preform 13 a′ is formed by increasing, if necessary, the shaft diameter of the billet 13 a″ in a predetermined range and forming a recess 52 at a joining-side end portion (end portion on the cup member 12 a side) by upset forging as illustrated in FIG. 5b . As described above, FIG. 5c is an illustration of an example of forming the recess 52 during forging and forming the inner diameter portion 53 in the opening end portion by turning. However, the recess 52 may maintain a forged surface. In that case, the recess 52 and the inner diameter portion 53 are integrally formed, and hence may not be clearly distinguished from each other.

After that, in the turning step S2 s, the outer diameter of the shaft member 13 a, the bearing mounting surface 14, the snap ring groove 15, an inner diameter portion 53 (inner diameter E), the joining end surface 51, and the outer diameter B thereof are formed by turning, as illustrated in FIG. 5c . Further, in the spline processing step S3 s, the spline shaft Sp is processed at the end portion on the opposite side to the recess 52 by rolling or press forming.

The outer diameter B of the joining end surface 50 of the cup member 12 a illustrated in FIG. 4b is set to an equal dimension for one joint size. Further, in the shaft member 13 a illustrated in FIG. 5c , which is used for a long stem shaft type, the outer diameter B of the joining end surface 51 located at the end portion on the cup member 12 a side is set to an equal dimension to the outer diameter B of the joining end surface 50 of the cup member 12 a irrespective of the shaft diameter and the outer peripheral shape. Still further, the joining end surface 51 of the shaft member 13 a is located at the position on the cup member 12 a side with respect to the bearing mounting surface 14.

Through the setting of dimensions as described above, the outer joint member 11 compatible with various vehicle types can be manufactured in such a manner that, while the cup member 12 a is prepared for common use, only the shaft member 13 a is manufactured to have a variety of shaft diameters, lengths, and outer peripheral shapes depending on vehicle types, and both the members 12 a and 13 a are welded to each other. Details of the preparation of the cup member 12 a for common use are described later.

Next, welding of the cup member 12 a and the shaft member 13 a is described with reference to FIG. 6 and FIG. 7. FIG. 6 is a schematic elevation view of a welding apparatus for illustrating a state before welding, and FIG. 7 is a schematic plan view of the welding apparatus for illustrating a state during welding.

As illustrated in FIG. 6, a welding apparatus 100 mainly comprises an electron gun 101, a rotation device 102, a chuck 103, a center 104, a tailstock 105, workpiece supports 106, a center 107, a case 108, and a vacuum pump 109.

The cup member 12 a and the shaft member 13 a being workpieces are placed on the workpiece supports 106 arranged inside the welding apparatus 100. The chuck 103 and the centering jig 107 arranged at one end of the welding apparatus 100 are coupled to the rotation device 102. The chuck 103 grips the cup member 12 a to rotate the cup member 12 a by the rotation device 102 under a state in which the center 107 has centered the cup member 12 a. The center 104 is integrally mounted to the tailstock 105 arranged at another end of the welding apparatus 100. Both the center 104 and the tailstock 105 are configured to reciprocate in the axial direction (lateral direction of FIG. 6).

A center hole of the shaft member 13 a is set on the center 104 so that the shaft member 13 a is centered. The vacuum pump 109 is connected to the case 108 of the welding apparatus 100. A “sealed space” herein refers to a space 111 defined by the case 108. The cup member 12 a and the shaft member 13 a are entirely received in the sealed space 111. The electron gun 101 is arranged at a position corresponding to the joining end surfaces 50 and 51 of the cup member 12 a and the shaft member 13 a. The electron gun 101 is configured to be approachable to and separable from the workpieces.

The operation of the welding apparatus 100 constructed as described above and the welding method are described below.

The cup member 12 a and the shaft member 13 a being workpieces are stocked at a place different from the place of the welding apparatus 100. The respective workpieces are taken out by, for example, a robot, are conveyed into the case 108 of the welding apparatus 100 opened to the air as illustrated in FIG. 6, and are set at predetermined positions of the workpiece supports 106. At this time, the center 104 and the tailstock 105 are retreated to the right side of FIG. 6, and hence a gap is formed between the joining end surfaces 50 and 51 of the cup member 12 a and the shaft member 13 a.

After that, a door (not shown) of the case 108 is closed, and the vacuum pump 109 is activated to reduce the pressure in the sealed space 111 defined in the case 108. Thus, the pressures in the recessed portion 50 b of the cup member 12 a and the recessed portions 52 and 53 of the shaft member 13 a are reduced as well.

When the pressure in the sealed space 111 is reduced to a predetermined pressure, the center 104 and the tailstock 105 are advanced to the left side as illustrated in FIG. 7 to eliminate the gap between the joining end surfaces 50 and 51 of the cup member 12 a and the shaft member 13 a. Thus, the cup member 12 a is centered by the center 107 and fixed by the chuck 103, whereas the shaft member 13 a is centered and supported by the center 104. After that, the workpiece supports 106 are moved away from the workpieces (12 a and 13 a). At this time, the distance between the workpiece supports 106 and the workpieces (12 a and 13 a) may be infinitesimal, and hence illustration of this distance is omitted from FIG. 7. As a matter of course, the welding apparatus 100 may have such a structure that the workpiece supports 106 are retreated downward greatly.

Although illustration is omitted, the electron gun 101 is then caused to approach the workpieces (12 a and 13 a) up to a predetermined position, and the workpieces (12 a and 13 a) are rotated to start pre-heating. As a pre-heating condition, unlike the welding condition, the temperature is set lower than the welding temperature by, for example, radiating an electron beam under a state in which the electron gun 101 is caused to approach the workpieces (12 a and 13 a) so as to increase the spot diameter. Through the pre-heating, the cooling rate at the welded portion after welding is reduced, thereby being capable of preventing a quenching crack. When a predetermined pre-heating time has elapsed, the electron gun 101 is retreated to a predetermined position, and radiates the electron beam from the outer side of the workpieces (12 a and 13 a) in the radial direction to start welding. When the welding is finished, the electron gun 101 is retreated, and the rotation of the workpieces (12 a and 13 a) is stopped.

Although illustration is omitted, the sealed space 111 is then opened to the air. Then, the center 104 and the tailstock 105 are retreated to the right side in the drawing sheet and the chuck 103 is opened under a state in which the workpiece supports 106 are raised to support the workpieces. After that, for example, the robot grips the workpieces (12 a and 13 a), takes the workpieces out of the welding apparatus 100, and places the workpieces into alignment on a cooling stocker. In this embodiment, the cup member 12 a and the shaft member 13 a are entirely received in the sealed space 111, and hence the configuration of the sealed space 111 defined in the case 108 can be simplified.

Specific conditions for welding are exemplified below.

The cup member 12 a having a carbon content of from 0.4% to 0.6% and the shaft member 13 a having a carbon content of 0.3% to 0.55% were used and welded to each other in the welding apparatus 100 under the condition that the pressure in the sealed space 111 defined in the case 108 was set to 6.7 Pa or less. In order to prevent rapid cooling after the welding to suppress excessive increase in hardness of the welded portion, a periphery including the joining end surfaces 50 and 51 of the cup member 12 a and the shaft member 13 a were soaked by pre-heating with the electron beam to have a temperature of from 300° C. to 650° C., and then electron beam welding was performed. As a result, the pre-heating time was able to be reduced to approximately one-half or less as compared to the case where the recess is not formed in the joining end surface, and a favorable welded portion satisfying the required strength was able to be obtained.

As a result, a welded portion having a projecting height from the welded surface (0.5 mm or less), which imposed no adverse effect on a product function, was obtained. Further, through the soaking by pre-heating, the hardness of the welded portion after completion of the welding was able to be kept within a range of from 200 HV to 500 HV, thereby being capable of attaining high welding strength and stable welding state and quality. Still further, welding was performed under the condition that the pressure in the sealed space 111 defined in the welding apparatus 100 was set to an atmospheric pressure or less, thereby being capable of suppressing the change in pressure in a hollow cavity portion during the welding. As a result, the blowing of a molten material and the entry of the molten material toward the radially inner side were able to be prevented. For example, a ventilation hole communicating with an inside of the cup member 12 a and with the recess 52 may be formed, and the space inside the cup member 12 a may be drawn to vacuum to the pressure of 1.3 Pa, and thereafter the joining surfaces may be brought into abutment against each other for welding.

Next, the ultrasonic flaw detection step is described with reference to FIG. 8 to FIG. 13.

Herein, FIG. 8 and FIG. 9 are a front view and a plan view, respectively, of an ultrasonic flaw-detection apparatus having a welded outer joint member mounted thereto. FIG. 8 corresponds to an illustration as viewed from the direction of the arrow VIII-VIII of FIG. 9. FIG. 10 and FIG. 11 are a front view and a plan view, respectively, of the ultrasonic flaw-detection apparatus during the ultrasonic flaw detection. FIG. 10 corresponds to an illustration as viewed from the direction of the arrow X-X of FIG. 11.

As illustrated in FIG. 8 and FIG. 9, an ultrasonic flaw-detection apparatus 120 mainly comprises a base 121, a water bath 122, a workpiece support 123, a workpiece holding member 124, a rotary drive device 125, a pressing device 135, and a drive positioning device 136 (see FIG. 9). The water bath 122 is mounted at the center of the base 121. The rotary drive device 125 is configured to rotate an intermediate product 11′ (hereinafter also referred to as “workpiece 11′”) of the outer joint member 11. The pressing device 135 is configured to press an axial end of the workpiece 11′. The drive positioning device 136 is configured to drive and position a probe.

The workpiece support 123 comprises support rollers 126 and 127 configured to allow the workpiece 11′ to be placed thereon in a freely rotatable manner. The support rollers 126 are arranged at a position close to the welded portion. The support rollers 127 are arranged near a center portion of the shaft section 13. As is apparent from FIG. 9, the support rollers 126 and 127 are constructed by pairs of rollers provided on both sides in the axial line of the shaft section 13 so that the shaft section 13 of the workpiece 11′ can be stably supported. The support rollers 126 and 127 are capable of adjusting the placement position of the workpiece 11′ in the axial direction (lateral direction of FIG. 8) and the radial direction (vertical direction of FIG. 8) in consideration of a joint size, dimensions, and weight balance of the workpiece 11′.

Further, the workpiece holding member 124 is mounted to the workpiece support 123 at a position displaced in a plane of FIG. 9 from an axial line of the workpiece 11′. The workpiece holding member 124 comprises a lever 128, and a workpiece holding roller 129 is arranged at an end portion of the lever 128. The lever 128 is pivotable in the plane of FIG. 9, and is movable in the vertical direction of FIG. 8.

The workpiece support 123 is mounted to a support 134 through intermediation of a linear-motion bearing 130 comprising rails 131 and linear guides 132, and is movable in the axial direction (lateral direction of FIG. 8 and FIG. 9). The support 134 is mounted to the base 121. The workpiece support 123 can be driven to be positioned at a desired position by an actuator (not shown) arranged on an outside of the water bath 122 through intermediation of a rod 133 coupled to an end portion (left end portion of FIG. 8 and FIG. 9).

The rotary drive device 125 comprises a rotary shaft 143 having a rotary disc 144 mounted thereto, and this rotary shaft 143 is driven to rotate by a motor (not shown) arranged on the outside of the water bath 122.

A mounting base 137 is arranged on an upper side of the ultrasonic flaw-detection apparatus 120. A base plate 145 for the pressing device 135 is mounted to the mounting base 137 through intermediation of a linear-motion bearing 138 comprising a rail 139 and a linear guide 140 so that the base plate 145 of the pressing device 135 is movable in the axial direction (lateral direction of FIG. 8 and FIG. 9). A rod 142 of a pneumatic cylinder 141 is coupled to an end portion of the base plate 145 so that the base plate 145 is driven, that is, axially moved by the pneumatic cylinder 141. The pressing device 135 is held in abutment against the axial end of the shaft section 13 of the workpiece 11′ through a free bearing 146.

As viewed in the plane of FIG. 9, the drive device 136 for a probe is arranged at a position displaced in the axial line of the workpiece 11′. This drive device 136 comprises actuators for the X-axis direction and the Y-axis direction so that a probe 147 is driven to be positioned in the X-axis direction and the Y-axis direction. An actuator 148 for the X-axis direction and an actuator 149 for the Y-axis direction are each an electric ball-screw type (ROBO cylinder), which is capable of performing positioning with high accuracy. The reference symbol 150 denotes a rail for a linear-motion bearing. The drive device 136 is arranged on the outside of the water bath 122, and the probe 147 and a holder 151 therefor are arranged in the water bath 122.

Next, the operation of the ultrasonic flaw-detection apparatus 120 having the above-mentioned configuration and the ultrasonic flaw detection step S6 k are described below.

First, the workpiece 11′ after welding is placed on the workpiece support 123 by a loader (not shown) (see FIG. 8 and FIG. 9). At this time, the workpiece support 123 is located at an appropriate interval from the rotary drive device 125 in the axial direction of the workpiece 11′, and the workpiece holding member 124 raises and pivots the lever 128 thereof so as to be substantially parallel to the axial line of the workpiece 11′. Further, the pressing device 135 and the drive device 136 for a probe wait at retreated positions.

After that, the lever 128 of the workpiece holding member 124 is pivoted so as to be substantially perpendicular to the axial line of the workpiece 11′, and then lowered to hold the workpiece 11′ from above (see FIG. 10). Then, water is supplied to the water bath 122. As described above, the ultrasonic flaw-detection apparatus 120 has the configuration of performing flaw detection under water, and hence ultrasonic waves are satisfactorily propagated. Thus, inspection can be performed with high accuracy.

Next, as illustrated in FIG. 10 and FIG. 11, the pneumatic cylinder 141 is driven to cause the pressing device 135 to be advanced and pressed against the axial end of the workpiece 11′, thereby pressing the opening rim of the cup section 12 of the workpiece 11′ against the rotary disc 144 of the rotary drive device 125. In conjunction with the advance of the pressing device 135, the workpiece support 123 is also moved toward the rotary drive device 125. Thus, the workpiece 11′ is positioned in the axial direction and the radial direction. In this state, the motor (not shown) of the rotary drive device 125 is activated, thereby rotating the workpiece 11′.

As illustrated in FIG. 11 with the outlined arrow, the drive device 136 is moved in the X-axis direction, and then moved in the Y-axis direction, thereby positioning the probe 147 at a flaw detection position. The probe 147 in this state is indicated by the broken line in FIG. 10. Then, the ultrasonic flaw detection is performed. After the completion of the ultrasonic flaw detection, water is drained from the water bath 122, and the workpiece 11′ is delivered from the ultrasonic flaw-detection apparatus 120 by the loader (not shown). In such a manner, the ultrasonic flaw detection is sequentially repeated on the workpiece 11′.

In order to reduce the cycle time of the ultrasonic flaw detection, it is desired that time-consuming supply and drainage of water be performed simultaneously with operations of the devices and the members, or at other timings in accordance therewith. Further, some of the operations of the devices and the members may be performed simultaneously with each other or in different orders as appropriate.

Details of the ultrasonic flaw detection are described with reference to FIG. 12a , FIG. 12b , and FIG. 13. All of FIG. 12a , FIG. 12b , and FIG. 13 are views as viewed from the arrow XII-XII of FIG. 10. FIG. 12a is an illustration of a non-defective welded product. FIG. 12b is an illustration of a defective welded product. FIG. 13 is a view for illustrating findings in the course of development.

The probe 147 is positioned at a flaw detection position away from the welded portion 49 by a predetermined distance. The flaw detection position is preset for each joint size. A transmission pulse G from the probe 147 is caused to obliquely enter from a surface of the workpiece 11′. A reflected echo having been received is displayed as waveforms, and the waveforms may be observed to determine a presence or absence of defectiveness (angle beam flaw detection method). The reference symbol θ1 denotes an incident angle, and the reference symbol θ2 denotes a refraction angle. In the case of the embodiment, the incident angle θ1 is about 20°, and the refraction angle θ2 is about 45°.

Herein, a presence or absence of the penetration defectiveness is mainly detected through detection of a position of a back bead. That is, workpieces having a penetration depth equal to or larger than a determination reference Wmin to reach a radially inner side are determined as non-defective welded products, and workpieces having a penetration depth smaller than the determination reference Wmin to terminate on a radially outer side are determined as defective welded products. In the illustrated example, the inner diameter portion 53 of the recess 52 formed in the joining end surface 51 is matched with the determination reference Wmin. The reference symbol E denotes an inner diameter of (the inner diameter portion 53 of) the recess 52, and also denotes an inner diameter of the joining end surface 51. The reference symbol Wa denotes a target penetration depth. Incidentally, after the welding, the welded portion 49 is formed on the radially outer side of the recess 52. As a result, a closed cavity is formed on the radially inner side of the welded portion 49. Thus, a back bead 491 cannot be visually confirmed from outside.

During the ultrasonic flaw detection, the workpiece 11′ is driven by the rotary drive device 125 to rotate. The probe 147 positioned at the flaw detection position away from the welded portion 49 by the predetermined distance collects data of the entire periphery of the workpiece 11′. In consideration of tolerance for displacement of the welding position, at the above-mentioned flaw detection position, first, data of a single rotation (360°) of the workpiece 11′ is collected. Then, the probe 147 is sequentially shifted in the axial direction at a minute pitch (for example, 0.5 mm) to collect data of a plurality of rotations (for example, five rotations). Based on those pieces of data, non-defective/defective determination is made. A threshold of a reflected echo to be used in the non-defective/defective determination is determined based on a welding pattern corresponding to the determination reference Wmin.

As already described above, in the joining end surface 50 of the cup member 12 a, there is formed the protruding surface 50 a which protrudes toward the radially inner side with respect to the inner diameter E of the joining end surface 51 of the shaft member 13 a. With the above-mentioned shape, the following advantages in the ultrasonic flaw detection can be obtained.

For easy understanding of the above-mentioned advantages, description is preferentially made of findings in the course of development, that is, the case in which an inner diameter D′ of the joining end surface 50 of the cup member 12 a is set to an equal dimension to the inner diameter E of the joining end surface 51 of the shaft member 13 a as illustrated in FIG. 13. In this case, the penetration depth is equal to or larger than the determination reference Wmin to reach the radially inner side, and hence the workpiece is to be determined as a non-defective welded product. However, when the transmission pulse G enters from the probe 147, due to the boundary surface of the back bead 491, which is perpendicular to the transmission pulse G, a reflected echo R reflected by this boundary surface is received by the probe 147. Although reflected echoes from the back bead 491 are scattered, the reflected echo R has a large echo height exceeding the threshold of the reflected echo for the non-defective/defective determination. Thus, determination that the welded product is defective is made. For this reason, it was proved that the determination as to whether the welded product was non-defective or defective was difficult.

Thus, in the embodiment, a measure is taken by forming the protruding surface 50 a, which protrudes toward the radially inner side with respect to the inner diameter E of the joining end surface 51 of the shaft member 13 a, in the joining end surface 50 of the cup member 12 a.

As illustrated in FIG. 12a , the non-defective welded product has sufficient penetration. In this case, the transmission pulse G from the probe 147 enters the cup section 12 through the back bead 491 having reached the radially inner side beyond the determination reference Wmin, and travels straight as it is. Alternatively, the transmission pulse G travels to the cup section 12 side by being reflected due to the inner diameter D of the cup section 12. Therefore, the probe 147 does not receive a reflected echo. That is, even when the transmission pulse G enters the back bead 491, the boundary surface of the back bead 491, which is perpendicular to the transmission pulse G, does not exist. Therefore, although a slightly-scattered reflected echo is generated, the reflected echo which may cause the detection error is not generated. Thus, the echo height of the reflected echo received by the probe 147 is equal to or less than the threshold, and hence determination that the welded product is non-defective is made.

As described above, when the protruding surface 50 a is formed on the joining end surface 50 of the cup member 12 a, the echo height of the reflected echo becomes lower. Thus, the accuracy in the inspection can be enhanced.

In the case of the defective welded product, as illustrated in FIG. 12b , a distal end of the bead 491 does not reach the determination reference Wmin due to the defective penetration. Thus, the transmission pulse G is reflected by the joining end surface 51 and a chamfered portion 51 a, and the scattered reflected echo R is received by the probe 147. The reflected echo R exceeds the threshold of the reflected echo for the non-defective/defective determination, and hence determination that the welded product is defective is made.

As described above, the protruding surface 50 a is formed on the joining end surface 50, and hence the echo heights of the reflected echoes can be clearly discriminated from each other. Thus, the determination as to whether the welded product is non-defective or defective can be made with high accuracy.

Dimensions of the protruding surface 50 a are set so that a relationship of S≥Q is established, where S [S=(E−D)/2] is a width of the protruding surface 50 a in a radial direction, and where Q is a height of the back bead 491 from the inner diameter E of the joining end surface 51 as illustrated in FIG. 12a . When this relationship is satisfied, the heights of the reflected echoes can be clearly discriminated from each other. Thus, the determination as to whether the welded product is non-defective or defective can be made with high accuracy. As long as the relationship of S≥Q is maintained, the dimensions of the protruding surface 50 a may be set as appropriate. The inner diameter E of the joining end surface 51 is also an inner diameter (of the inner diameter portion 53) of the recess 52.

In the ultrasonic flaw-detection apparatus 120, the operation of loading the workpiece 11′, the supply and drainage of water, the ultrasonic flaw detection, and the operation of unloading the workpiece can be performed in conjunction with each other, and the ultrasonic flaw detection can be automated. Thus, accuracy, operability, and efficiency in the inspection can be enhanced, which is suited to the inspection on the welded portion of the outer joint member of the constant velocity universal joint being a mass-produced product.

Further, in the ultrasonic flaw detection, with the base configuration in which the outer diameter B of the joining end surface 50 of the cup member 12 a is set to an equal dimension for each joint size, setup and replacement operations with respect to the outer joint members 11 having the different product numbers are reduced. Thus, the efficiency in the inspection can be further enhanced.

Still further, flaw detection is performed under water, and hence ultrasonic waves are satisfactorily propagated. Thus, inspection can be performed with much higher accuracy. In addition, through employment of the shape of the welded portion, in which the protruding surface 50 a is formed on the joining end surface 50, the echo heights of the reflected echoes can clearly be discriminated from each other. Thus, the determination as to whether the welded product is non-defective or defective can be made with high accuracy.

Next, standardization of a product type of the cup member is additionally described while exemplifying a shaft member having a product number different from that of the above-mentioned shaft member 13 a of the long stem type illustrated in FIG. 5 c.

A shaft member 13 b illustrated in FIG. 14 and FIG. 15 is used as a general stem type on the inboard side. The shaft member 13 b has the joining end surface 51 to be brought into abutment against the joining end surface 50 (see FIG. 4b ) of the bottom portion 12 a 2 (short shaft section 12 a 3) of the cup member 12 a. The outer diameter B and the inner diameter E of the joining end surface 51 are set to the equal dimensions to the outer diameter B and the inner diameter E of the joining end surface 51 of the shaft member 13 a of the long stem type illustrated in FIG. 5 c.

Also in this case, the inner diameter D of the joining end surface 50 of the cup member 12 a is set smaller than the inner diameter E of the joining end surface 51 of the shaft member 13 b. As a result, on the joining end surface 50 of the cup member 12 a, the protruding surface 50 a protruding to the radially inner side with respect to the inner diameter E of the joining end surface 51 of the shaft member 13 b is formed. The joining end surfaces 50 and 51 having such shape are brought into abutment against each other to be welded so that the cup member 12 a and the shaft member 13 b are joined to each other.

The shaft member 13 b is used as the general stem type on the inboard side. Accordingly, the shaft member 13 b comprises a shaft section with a small length, and a sliding bearing surface 25 formed on an axial center portion thereof, and a plurality of oil grooves 26 are formed in the sliding bearing surface 25. The spline shaft Sp and the snap ring groove 48 are formed in an end portion on the side opposite to the cup member 12 a side. As described above, even when there are differences in types, such as the general length stem type and the long stem type, and shaft diameters and outer peripheral shapes vary in each vehicle type, the outer diameter B of the joining end surface 51 of the shaft member 13 a or 13 b is set to an equal dimension.

The outer diameter B of the joining end surface 50 of the cup member 12 a and the joining end surface 51 of the shaft member 13 a or 13 b is set to an equal dimension for each joint size. Thus, the cup member prepared for common use for each joint size, and the shaft member having a variety of specifications of the shaft section for each vehicle type can be prepared in a state before heat treatment. Further, the intermediate component of each of the cup member 12 a and the shaft member 13 a or 13 b can be assigned with a product number for management. Even when standardizing product types of the cup member 12 a, various types of the outer joint members satisfying requirements can be produced quickly through combination of the cup member 12 a and the shaft member 13 a or 13 b having a variety of specifications of the shaft section for each vehicle type. Therefore, standardization of a product type of the cup member 12 a can reduce cost and alleviate a burden of production management.

The standardization of the product type of the cup member is described above by taking the differences in types, such as the general length stem type and the long stem type, as an example for easy understanding, but the present invention is not limited thereto. The same applies to standardization of the product type of the cup member for shaft members having a variety of specifications of the shaft section for each vehicle type among the general length stem types, and for shaft members having a variety of specifications of the shaft section for each vehicle type among the long stem types.

An example of standardization of a product type of the cup member is illustrated in FIG. 16.

As illustrated in FIG. 16, the cup member is prepared for common use for one joint size, and is assigned with, for example, a product number C001 for management. In contrast, the shaft member has a variety of specifications of the shaft section for each vehicle type, and is assigned with, for example, a product number S001, S002, or S (n) for management. For example, when the cup member assigned with the product number C001 and the shaft member assigned with the product number S001 are combined and welded to each other, the outer joint member assigned with a product number A001 can be produced.

Thus, owing to standardization of a product type of the cup member, it is possible to reduce cost and to alleviate a burden of production management. In the standardization of a product type, the cup member is not limited to one type for one joint size, that is, not limited to one type assigned with a single product number. For example, the cup member comprises cup members of a plurality of types (assigned with a plurality of product numbers, respectively) that are prepared for one joint size based on different specifications of a maximum operating angle, and are each prepared so that the outer diameter B of the joining end surface of each of those cup members has an equal dimension.

Next, a second embodiment of the outer joint member is described with reference to FIG. 17a to FIG. 17c and FIG. 18.

FIG. 17a is a partial sectional front view of the outer joint member. FIG. 17b is an enlarged view of a portion “b” of FIG. 17a . FIG. 17c is a view for illustrating a state before welding in FIG. 17b . FIG. 18 is a vertical sectional view for illustrating the cup member before welding. FIG. 17a to FIG. 17c correspond to FIG. 2a to FIG. 2c . As is clear from comparison of FIG. 17a to FIG. 17c and FIG. 2a to FIG. 2c , the second embodiment is different from the above-mentioned first embodiment in the form of the radially inner side of the joining end surface of the cup member. Other configurations are the same as those in the first embodiment. Thus, parts that have the same function as those of the first embodiment are denoted by the same reference symbols except for the subscripts, and redundant description is omitted. As a matter of course, as illustrated in FIG. 17b with the broken parallel oblique lines, the second embodiment is also the same as the first embodiment in that an assumed range S₁ of the center segregation is confined within the radially inner side to prevent the interference with the welded portion 49.

As illustrated in FIG. 17c and FIG. 18, a joining end surface 50 ₁ formed on a short shaft section 12 a 3 ₁ of a cup member 12 a ₁ is annular, and a projecting portion 50 b ₁ is formed on the radially inner side. In this case, a diameter D₁ of the annular joining end surface 50 ₁ on the radially inner side corresponds to the inner diameter D of the joining end surface 50 of the cup member 12 a of the first embodiment of the outer joint member. A portion of the joining end surface 50 ₁ on the radially inner side protrudes toward the radially inner side with respect to the inner diameter E of the joining end surface 51 of the shaft member 13 a. This protruding portion is referred to as a protruding surface 50 a ₁ as in the first embodiment. As in the first embodiment, the shaft member 13 a has the recess 52 on the radially inner side of the joining end surface 51. In order to prevent hindrance in abutment of the joining end surfaces 50 ₁ and 51, the height of the projecting portion 50 b ₁ of the cup member 12 a ₁, that is, a distance from the joining end surface 50 ₁ to the end surface of the projecting portion 50 b ₁ is set smaller than the depth of the recess 52.

The cup member 12 a ₁ can be formed by turning an end surface of the short shaft section 12 a 3′ of the preform 12 a′ (FIG. 4a ) for the cup member of the first embodiment after ironing at only a portion of the joining end surface 50 ₁ on the radially outer side. Thus, the time for the turning can be reduced, with good material yield. As a matter of course, the projecting portion 50 b ₁ on the radially inner side can also be subjected to turning. However, the number of steps can be reduced by maintaining the forged surface as it is.

Other configurations and operations, that is, the overview of the respective steps, the states of the cup member and the shaft member in the main processing steps, the preparation of the cup member for common use, the welding method, the ultrasonic flaw detection, the standardization of the product type, the configuration of the outer joint member, and the like as described above in relation to the first embodiment of the outer joint member are also applicable to the second embodiment of the outer joint member.

FIG. 19 is an illustration of a second embodiment of a manufacturing method of the outer joint member.

In the second embodiment, the heat treatment step for the cup member, which is involved in the heat treatment step S7 in FIG. 3, is provided before the welding step S6 and named “heat treatment step S5 c”, to thereby prepare the cup member as a finished product. Other than this point, the matters described above in relation to the first embodiment of the manufacturing method, that is, the overview of the respective steps, the states of the cup member and the shaft member in the main processing steps, the preparation of the cup member for common use, the welding method, the ultrasonic flaw detection, the standardization of the product type, the configuration of the outer joint member, and the like are also applicable to the second embodiment.

As illustrated in FIG. 4b , the cup member 12 a has a shape extending from the joining end surface 50 to the large-diameter cylindrical portion 12 a 1 via the bottom portion 12 a 2, and the portions to be subjected to heat treatment that involves quenching and tempering are the track grooves 30 and the cylindrical inner peripheral surface 42 located at the inner periphery of the cylindrical portion 12 a 1. Therefore, the cup member 12 a generally has no risk of thermal effect on the heat-treated portion during the welding. For this reason, the cup member 12 a is subjected to heat treatment before the welding to be prepared as a finished product. Such manufacturing steps are suitable in practical use.

The cup member 12 a is subjected to heat treatment for preparing the cup member 12 a as a finished product, and is therefore assigned with a product number indicating a finished product for management. Thus, the standardization of the product type of the cup member 12 a remarkably reduces the cost and alleviates the burden of production management. Further, the cup member 12 a can be manufactured solely until the cup member 12 a is completed as a finished product through the forging, turning, and heat treatment. Thus, the productivity is enhanced by virtue of reduction of setups and the like as well.

With regard to FIG. 16 for illustrating the example of standardization of the product type of the cup member described above in relation to the first embodiment of the manufacturing method, only the product number of the cup member in FIG. 16 is changed to the product number indicating a finished product, whereas the product numbers of the shaft member and the outer joint member are the same as those of the first embodiment of the manufacturing method. Therefore, description thereof is omitted herein.

FIG. 20 is an illustration of a third embodiment of a manufacturing method of the outer joint member.

In the third embodiment, the heat treatment steps for the cup section and the shaft section, which are involved in the heat treatment step S7 in FIG. 3 described above in relation to the first embodiment, and the grinding step S8 for the shaft section in FIG. 3 are provided before the welding step S6 in the sequence and named “heat treatment step S5 c for cup member”, “heat treatment step S4 s for shaft member”, and “grinding step S5 s”. Thus, both the cup member and the shaft member are prepared as finished products. Other matters, that is, the overview of the respective steps, the states of the cup member and the shaft member in the main processing steps, the preparation of the cup member for common use, the welding method, the ultrasonic flaw detection, the standardization of the product type, the configuration of the outer joint member, and the like described in relation to the first embodiment are also applicable to the third embodiment.

After the spline processing step S3 s, a hardened layer having a hardness of approximately from 50 HRC to 62 HRC is formed in a predetermined range of the outer peripheral surface of the shaft member by induction quenching in the heat treatment step S4 s. Heat treatment is not performed on a predetermined portion in the axial direction, which includes the joining end surface 51. The heat treatment for the cup member, the assignment of the product number, and the like are the same as those of the second embodiment on the manufacturing method, and redundant description is therefore omitted herein.

After the heat treatment step S4 s, the shaft member is transferred to the grinding step S5 s so that the bearing mounting surface 14 and the like are finished. Thus, the shaft member is obtained as a finished product. Then, the shaft member is assigned with a product number indicating a finished product for management. The manufacturing steps of the third embodiment are suitable in a case of a cup member and a shaft member having shapes and specifications with no risk of thermal effect on the heat-treated portion during the welding.

In the manufacturing steps of the third embodiment, both the cup member and the shaft member can be assigned with product numbers indicating finished products for management. Thus, the standardization of the product type of the cup member further remarkably reduces the cost and alleviates the burden of production management. Further, the cup member and the shaft member can be manufactured independently of each other until the cup member and the shaft member are completed as finished products through the forging, turning, heat treatment, grinding after heat treatment, and the like. Thus, the productivity is further enhanced by virtue of reduction of setups and the like as well.

In the case of the third embodiment of the manufacturing method, with regard to FIG. 16 for illustrating the example of standardization of the product type of the cup member described above in relation to the first embodiment, the product numbers of the cup member and the shaft member in FIG. 16 are changed to the product numbers indicating finished products. The outer joint member is the same as that of the first embodiment of the manufacturing method. Therefore, description thereof is omitted herein. Note that, the cup member and the shaft member to be prepared as finished products are not limited to the cup member and the shaft member subjected to finishing such as the above-mentioned grinding after heat treatment or cutting after quenching, and encompass a cup member and a shaft member in a state in which the heat treatment is completed while the finishing is uncompleted.

As described with regard to the standardization of the product type, the cup member is not limited to one type for one joint size, that is, not limited to one type assigned with a single product number. The cup member encompasses, for example, cup members of a plurality of types (assigned with a plurality of product numbers, respectively) that are prepared for one joint size based on different specifications of a maximum operating angle, and are also prepared so that the outer diameters B of the above-mentioned joining end surfaces of the cup members are set to equal dimensions. In addition, the cup member encompasses, for example, cup members of a plurality of types (assigned with a plurality of product numbers, respectively) that are prepared for one joint size in order to achieve management of the cup members in a plurality of forms including intermediate components before heat treatment and finished components in consideration of the joint function, the circumstances at the manufacturing site, the productivity, and the like, and are also prepared so that the outer diameters B of the above-mentioned joining end surfaces of the cup members are set to equal dimensions.

Next, a third embodiment of the outer joint member is described with reference to FIG. 21 and FIG. 22.

Herein, parts that have the same function as those of the first embodiment of the outer joint member are denoted by the same reference symbols, and only main points are described.

A plunging type constant velocity universal joint 10 ₂ illustrated in FIG. 21 is a tripod type constant velocity universal joint (TJ), and comprises an outer joint member 11 ₂, an inner joint member 16 ₂, and rollers 19 serving as torque transmitting elements. The outer joint member 11 ₂ comprises a cup section 12 ₂ and the long stem section 13 that extends from a bottom of the cup section 12 ₂ in the axial direction. The inner joint member 16 ₂ comprises a tripod member 17 comprising three equiangular leg shafts 18 configured to support the rollers 19 in a freely rotatable manner, and is housed along an inner periphery of the cup section 12 ₂ of the outer joint member 11 ₂. The rollers 19 are arranged between the outer joint member 11 ₂ and the inner joint member 16 ₂, and configured to transmit torque therebetween.

Similarly to the first embodiment of the outer joint member, the inner ring of the support bearing 6 is fixed to the outer peripheral surface of the long stem section 13, and the outer ring of the support bearing 6 is fixed to the transmission case with the bracket (not shown). The outer joint member 11 ₂ is supported by the support bearing 6 in a freely rotatable manner, and thus the vibration of the outer joint member 11 ₂ during driving or the like is prevented as much as possible.

As illustrated in FIG. 22, the outer joint member 11 ₂ comprises a cup section 12 ₂ and the long stem section 13. The cup section 12 ₂ has a bottomed cylindrical shape that is opened at one end, and has track grooves 30 ₂, on which the rollers 19 are caused to roll, formed at three equiangular positions on an inner peripheral surface 31 ₂. The long stem section 13 extends from the bottom of the cup section 12 ₂ in the axial direction and comprises the spline shaft Sp serving as the torque transmitting coupling portion formed at the outer periphery of the end portion on the side opposite to the cup section 12 ₂.

The outer joint member 11 ₂ is formed by welding the cup member 12 a ₂ serving as the cup section 12 ₂ and the shaft member 13 a serving as the long stem section 13 to each other.

The cup member 12 a ₂ is an integrally-formed product having a cylindrical portion 12 a 1 ₂ and a bottom portion 12 a 2 ₂, and has track grooves 130 and an inner peripheral surface 131 formed at the inner periphery of the cylindrical portion 12 a 1 ₂. A short shaft section 12 a 3 ₂ is formed at the bottom portion 12 a 2 ₂. A boot mounting groove 32 is formed at an outer periphery of the cup member 12 a ₂ on the opening side.

In the shaft member 13 a, the bearing mounting surface 14 and the snap ring groove 15 are formed at the outer periphery on the cup member 12 a ₂ side, and the spline shaft Sp is formed at an end portion on the side opposite to the cup member 12 a ₂.

A joining end surface 50 ₂ formed at the short shaft section 12 a 3 ₂ of the cup member 12 a ₂ and the joining end surface 51 formed at the end portion of the shaft member 13 a on the cup member 12 a ₂ side are brought into abutment against each other, and are welded to each other by radiating an electron beam from the radially outer side. As is well known, the welded portion 49 comprises metal that is molten and solidified during welding, that is, the molten metal, and the heat-affected portion in the periphery thereof.

Similarly to the first embodiment of the outer joint member, the outer diameters B of the joining end surface 50 ₂ and the joining end surface 51 are set to equal dimensions for each joint size. The welded portion 49 is formed on the cup member 12 a ₂ side with respect to the bearing mounting surface 14 of the shaft member 13 a, and hence the bearing mounting surface 14 and the like can be processed in advance so that post-processing after welding can be omitted. Further, due to the electron beam welding, burrs are not generated at the welded portion. Thus, post-processing for the welded portion can also be omitted, which can reduce the manufacturing cost.

The matters described in relation to the first and second embodiments of the outer joint member and the first to third embodiments of the manufacturing method are also applicable to the third embodiment of the outer joint member.

Herein, with regard to setting of the outer diameters B of the joining end surface 50, 50 ₁, or 50 ₂ of the cup member 12 a, 12 a ₁, or 12 a ₂ and the protruding surfaces 50 a and 50 a ₁ to the equal dimension for each joint size, the cup member 12 a, 12 a ₁, or 12 a ₂ is not limited to one type for one joint size, that is, not limited to one type assigned with a single product number.

For example, the cup member encompasses cup members of a plurality of types (assigned with a plurality of product numbers, respectively) that are prepared for one joint size based on different specifications of a maximum operating angle, and are also prepared so that the outer diameters of the above-mentioned joining end surfaces of the cup members are set to equal dimensions and that the protruding surfaces are formed into the same shape.

In addition, the cup member encompasses, for example, cup members of a plurality of types (assigned with a plurality of product numbers, respectively) that are prepared for one joint size in order to achieve management of the cup members in a plurality of forms including intermediate components before heat treatment and finished components after heat treatment in consideration of the joint function, the circumstances at the manufacturing site, the productivity, and the like, and are also prepared so that the outer diameters of the above-mentioned joining end surfaces of the cup members are set to equal dimensions and that the protruding surfaces are formed into the same shape.

Further, setting the outer diameter B of the joining end surface 50, 50 ₁, or 50 ₂ of the cup member 12 a, 12 a ₁, or 12 a ₂ to an equal dimension for each joint size, or forming the protruding surfaces 50 a and 50 a ₁ into the same shape for each joint size may be applied also to different types of constant velocity universal joints.

For example, setting outer diameters of the joining end surfaces of a tripod type constant velocity universal joint and a double-offset constant velocity universal joint to equal dimensions, and forming the protruding surface into the same shape on the inboard side are also encompassed. Further, setting outer diameters of the joining end surfaces of a Rzeppa type constant velocity universal joint and an undercut-free constant velocity universal joint to equal dimensions, and forming the protruding surface into the same shape on the outboard side are also encompassed. Further, setting the outer diameters of the joining end surfaces of the constant velocity universal joints on the inboard side and the outboard side to equal dimensions, and forming the protruding surface into the same shape on the inboard side and the outboard side are also possible.

At least one of the cup member 12 a, 12 a ₁, or 12 a ₂ and the shaft member 13 a or 13 b before the welding may be prepared as an intermediate component without performing heat treatment. In this case, the heat treatment and finishing such as grinding and quenched-steel cutting work are performed after welding. Thus, this configuration is suited to the cup members 12 a, 12 a ₁, and 12 a ₂ and the shaft members 13 a and 13 b having such shapes and specifications that the hardness of the heat-treated portion may be affected by temperature rise at the periphery due to heat generated during welding after heat treatment. The intermediate component is assigned with a product number for management.

Further, at least one of the cup member 12 a, 12 a ₁, or 12 a ₂ and the shaft member 13 a or 13 b before the welding may be prepared as a finished component subjected to heat treatment. The finished component subjected to heat treatment is a finished component subjected to the heat treatment and the finishing such as grinding after the heat treatment or quenched-steel cutting work. In this case, it is possible to obtain the cup member 12 a, 12 a ₁, or 12 a ₂ prepared as the finished component for common use for each joint size, and the shaft members having a variety of specifications of the shaft section for each vehicle type. Thus, the cup members and the shaft members can each be assigned with a product number for management. Therefore, the cost is significantly reduced through the standardization of a product type of the cup members 12 a, 12 a ₁, and 12 a ₂, and the burden of production management is significantly alleviated.

Further, the cup members 12 a, 12 a ₁, and 12 a ₂ prepared for common use and the shaft members 13 a and 13 b having a variety of specifications of the shaft section can be manufactured separately until the cup members and the shaft members are formed into the finished components subjected to the finishing such as forging, turning, heat treatment, grinding, and quenched-steel cutting work. Further, as well as reduction of setups and the like, the enhancement of productivity is achieved. However, the cup members 12 a, 12 a ₁, and 12 a ₂ and the shaft members 13 a and 13 b as the finished components are not limited to members subjected to finishing such as the grinding after the heat treatment or the quenched-steel cutting work as described above. The cup members 12 a, 12 a ₁, and 12 a ₂ and the shaft members 13 a and 13 b assuming a state after completion of heat treatment and before being subjected to the finishing are encompassed.

The effects of the above-mentioned embodiments of the present invention are summarized and described below.

The outer joint member 11, 11 ₁, or 11 ₂ of the embodiment is an outer joint member of a constant velocity universal joint, which is manufactured by joining the cup member 12 a, 12 a ₁, or 12 a ₂ and the shaft member 13 a or 13 b.

The cup member 12 a, 12 a ₁, or 12 a ₂ has a bottomed cylindrical shape that is opened at one end, and comprises the cylindrical portion 12 a 1, 12 a 1 ₁, or 12 a 1 ₂, the bottom portion 12 a 2, 12 a 2 ₁, or 12 a 2 ₂, and the short shaft portion 12 a 3, 12 a 3 ₁, or 12 a 3 ₂ protruding from the bottom portion 12 a 2, 12 a 2 ₁, or 12 a 2 ₂. The short shaft portion 12 a 3, 12 a 3 ₁, or 12 a 3 ₂ has a solid shaft shape and comprises the joining end surface 50, 50 ₁, or 50 ₂ at an end portion thereof. The shaft member 13 a or 13 b has a solid shaft shape and comprises the joining end surface 51 at one end thereof. The joining end surface 50, 50 ₁, or 50 ₂ of the cup member 12 a, 12 a ₁, or 12 a ₂ and the joining end surface 51 of the shaft member 13 a or 13 b are brought into abutment against each other and welded through radiation of a high energy intensity beam from the radially outer side to form the annular welded portion 49. With this, the interference of the center segregation with the welded portion 49 is prevented. Through formation of the welded portion 49 into an annular shape, the welded portion 49 can be arranged on the radially outer side avoiding the center segregation. Thus, the strength and welding quality are improved.

According to the manufacturing method of the embodiment, when the outer joint member 11, 11 ₁, or 11 ₂ of a constant velocity universal joint is to be manufactured, the cup member 12 a, 12 a ₁, or 12 a ₂ is formed through forging. The forging comprises: upsetting the billet 60 having a columnar shape successively in a plurality of stages; extruding the cylindrical portion 12 a 1, 12 a 1 ₁, or 12 a 1 ₂ and the short shaft portion 12 a 3, 12 a 3 ₁, or 12 a 3 ₂; and ironing the cylindrical portion 12 a 1, 12 a 1 ₁, or 12 a 1 ₂. The joining end surface 50, 50 ₁, or 50 ₂ of the cup member 12 a, 12 a ₁, or 12 a ₂ and the joining end surface 51 of the shaft member 13 a or 13 b are brought into abutment against each other and welded through radiation of a high energy intensity beam from the radially outer side to form the welded portion 49 having an annular shape. Through the upsetting in the plurality of stages, the billet edge can be moved to the radially outer side as much as possible.

In the die 62 to be used in the course of the upsetting, an inner diameter is larger than an outer diameter of the billet 60 in a first region corresponding to an opening side of the cup member 12 a, 12 a ₁, or 12 a ₂, and an inner diameter is gradually reduced in a second region corresponding to a bottom side of the cup member 12 a, 12 a ₁, or 12 a ₂. Then, a plurality of dies gradually increased in inner diameters in the first region are sequentially used. With this, in the course of the upsetting, the billet 60 is increased in diameter in the region corresponding to the opening side of the cup member 12 a, 12 a ₁, or 12 a ₂, and the region corresponding to the bottom side of the cup member 12 a, 12 a ₁, or 12 a ₂ is narrowed. Through the narrowing, a flow of the material toward the radially outer side is prevented, thereby being capable of confining the center segregation of the billet within the radially inner side.

With regard to the second region of the die 62, the gradually reduced diameter is, as a specific example, a recessed arc shape 64A, a taper shape 64B, or a combined shape 64C of the arc and the taper in sectional view.

The extruding comprises the forward extrusion for forming the short shaft portion 12 a 3, 12 a 3 ₁, or 12 a 3 ₂ and the backward extrusion for forming the cylindrical portion 12 a 1, 12 a 1 ₁, or 12 a 1 ₂. At this time, when the second region narrowed in the course of the upsetting is to be subjected to the forward extrusion to form the short shaft portion 12 a 3, 12 a 3 ₁, or 12 a 3 ₂, the fiber flow in the axial direction is formed. With this, an increase in diameter (lateral expansion) is suppressed as much as possible, thereby being capable of confining the narrowed center segregation within the center portion.

The outer joint member of a constant velocity universal joint manufactured by the above-mentioned method is improved in strength and welding quality of the welded portion.

The embodiments of the present invention are described above with reference to the attached drawing. However, the present invention is not limited to the embodiments described herein and illustrated in the attached drawings. The present invention can be carried out with various modifications within the range of not departing from the scope of claims.

The case of employing the electron beam welding is described as an example. However, the present invention is applicable not only to the case of the electron beam welding but also to the case of employing laser welding or other welding through use of a high energy intensity beam.

Further, the double-offset type constant velocity universal joint and the tripod type constant velocity universal joint are exemplified as the plunging type constant velocity universal joint. However, the present invention is also applicable to an outer joint member of a cross-groove type constant velocity universal joint or other plunging type constant velocity universal joint, and to an outer joint member of a fixed type constant velocity universal joint. Further, the case of applying the present invention to the outer joint member of the constant velocity universal joint constructing a drive shaft is described as an example. However, the present invention is also applicable to an outer joint member of a constant velocity universal joint constructing a propeller shaft.

REFERENCE SIGNS LIST

-   10 plunging type constant velocity universal joint -   11, 11 ₁, 11 ₂ outer joint member -   12, 12 ₁, 12 ₂ cup section -   12 a, 12 a ₁, 12 a ₂ cup member -   12 a 1, 12 a 1 ₁, 12 a 1 ₂ cylindrical portion -   12 a 2, 12 a 2 ₂, 12 a 2 ₂ bottom portion -   12 a 3, 12 a 3 ₁, 12 a 3 ₂ short shaft section -   13 shaft section (long stem section) -   13 a, 13 b shaft member -   14 bearing mounting surface -   16 inner joint member -   17 tripod member -   19 torque transmitting element (roller) -   41 torque transmitting element (ball) -   49 welded portion -   50, 50 ₁, 50 ₂ joining end surface of cup member -   50 a protruding surface -   50 b recessed portion -   50 b ₁ projecting portion -   51 joining end surface of shaft member -   52 recess -   53 inner diameter portion (of joining end surface 51) -   60 billet -   62A to 62D die -   64A arc-shaped section -   64B taper-shaped section -   64C section having combined shape of arc and taper -   66A to 66D punch -   68 ironing die -   100 welding apparatus -   120 ultrasonic flaw-detection apparatus -   S, S₁ assumed range of center segregation 

The invention claimed is:
 1. A method of manufacturing an outer joint member of a constant velocity universal joint, the method comprising: forming a cup member by forging, the forging comprising: upsetting a billet having a columnar shape successively in a plurality of stages; extruding a cylindrical portion and a shaft portion; and ironing the cylindrical portion; and joining the cup member and a shaft member to form the outer joint member, wherein the cup member has a bottomed cylindrical shape that is opened at an end on one side in an axial direction, and comprises the cylindrical portion, a bottom portion, and the shaft portion protruding from the bottom portion toward another side in the axial direction, the shaft portion has a solid shaft shape, and comprises an annular joining end surface at an end portion thereof, the shaft member has a solid shaft shape, and comprises an annular joining end surface at one end thereof, the joining comprises bringing the annular joining end surface of the cup member and the annular joining end surface of the shaft member into abutment against each other and welding the annular joining end surface of the cup member and the annular joining end surface of the shaft member to form a welded portion having an annular shape, in a course of the upsetting, a diameter of a first region of the billet corresponding to an opening side of the cup member is increased and a second region corresponding to a bottom side of the cup member is narrowed, the welded portion is formed on a cup member side with respect to a bearing mounting surface formed on the shaft member, and the welded portion formed by the welding is free from interference with center segregation of the cup member.
 2. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 1, wherein the welding is performed through radiation of a high energy intensity beam from a radially outer side.
 3. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 2, wherein the upsetting comprises: using a die having an inner diameter that is larger than an outer diameter of the billet in the first region corresponding to the opening side of the cup member, and an inner diameter that is gradually reduced in the second region corresponding to the bottom side of the cup member, and sequentially using a plurality of dies, including the die, having gradually increased inner diameters in the first region to increase a diameter of the billet in the first region corresponding to the opening side of the cup member and to narrow the billet in the second region corresponding to the bottom side of the cup member.
 4. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 2, wherein the extruding comprises performing forward extrusion for forming the shaft portion and backward extrusion for forming the cylindrical portion.
 5. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 1, wherein the upsetting comprises: using a die having an inner diameter that is larger than an outer diameter of the billet in the first region corresponding to the opening side of the cup member, and an inner diameter that is gradually reduced in the second region corresponding to the bottom side of the cup member, and sequentially using a plurality of dies, including the die, having gradually increased inner diameters in the first region to increase a diameter of the billet in the first region corresponding to the opening side of the cup member and to narrow the billet in the second region corresponding to the bottom side of the cup member.
 6. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 5, wherein a vertical section of the die in the second region has a recessed arc shape.
 7. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 6, wherein the extruding comprises performing forward extrusion for forming the shaft portion and backward extrusion for forming the cylindrical portion.
 8. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 6, wherein the extruding comprises performing forward extrusion for forming the shaft portion, and when the second region narrowed in the course of the upsetting is subjected to the forward extrusion to form the shaft portion, a fiber flow in the axial direction is formed.
 9. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 5, wherein a vertical section of the die in the second region has a taper shape.
 10. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 9, wherein the extruding comprises performing forward extrusion for forming the shaft portion and backward extrusion for forming the cylindrical portion.
 11. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 9, wherein the extruding comprises performing forward extrusion for forming the shaft portion, and when the second region narrowed in the course of the upsetting is subjected to the forward extrusion to form the shaft portion, a fiber flow in the axial direction is formed.
 12. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 5, wherein a vertical section of the die in the second region has a combined shape of a recessed arc and a taper.
 13. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 12, wherein the extruding comprises performing forward extrusion for forming the shaft portion and backward extrusion for forming the cylindrical portion.
 14. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 12, wherein the extruding comprises performing forward extrusion for forming the shaft portion, and when the second region narrowed in the course of the upsetting is subjected to the forward extrusion to form the shaft portion, a fiber flow in the axial direction is formed.
 15. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 5, wherein the extruding comprises performing forward extrusion for forming the shaft portion, and when the second region narrowed in the course of the upsetting is subjected to the forward extrusion to form the shaft portion, a fiber flow in the axial direction is formed.
 16. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 5, wherein the extruding comprises performing forward extrusion for forming the shaft portion and backward extrusion for forming the cylindrical portion.
 17. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 1, wherein the extruding comprises performing forward extrusion for forming the shaft portion and backward extrusion for forming the cylindrical portion.
 18. The method of manufacturing an outer joint member of a constant velocity universal joint according to claim 17, wherein, when the second region narrowed in the course of the upsetting is subjected to the forward extrusion to form the shaft portion, a fiber flow in the axial direction is formed. 